My research, like so much research in social psychology, demonstrates that we humans are experts at using reasoning to find evidence for whatever conclusions we want to reach. We are terrible at searching for contradictory evidence. Science works because our peers are so darn good at finding that contradictory evidence for us. Social science — at least my corner of it — is broken because there is nobody to look for contradictory evidence regarding sacralized issues, particularly those related to race, gender, and class. I urged my colleagues to increase our ideological diversity not for any moral reason, but because it will make us better scientists. You do not have that problem in economics where the majority is liberal but there is a substantial and vocal minority of libertarians and conservatives. Your field is healthy, mine is not.
Do you think I was wrong to call for my professional organization to seek out a modicum of ideological diversity?

On a related note, the IMF review of why the institution failed to warn of the global financial crisis identified a lack of intellectual diversity as being among the factors responsible (PDF):

Several cognitive biases seem to have played an important role. Groupthink refers to the tendency among homogeneous, cohesive groups to consider issues only within a certain paradigm and not challenge its basic premises (Janis, 1982). The prevailing view among IMF staff—a cohesive group of macroeconomists—was that market discipline and self-regulation would be sufficient to stave off serious problems in financial institutions. They also believed that crises were unlikely to happen in advanced economies, where “sophisticated” financial markets could thrive safely with minimal regulation of a large and growing portion of the financial system.